Enteropathogenic E. coli and other coliforms in marine fish

One hundred and twenty six samples of marine fish (96 from landing centre and 30 from retail market) and swabs from deck surfaces of 34 fishing boats were examined for coliforms including enteropathogenic E. Coli. Forty out of 96 fish samples from landing centre, 24 out of 30 from retail market and 11 out of 34 fishing boats revealed coliforms. On further tests, 5, 7 and 4 coliform isolates from the three groups respectively were found to be E. coli. Two of the E. coli. isolated, one from sciaenids and one from cat fish, were found to be enteropathogenic serotypes 055 and 0111. Enteropathogenic serotypes of E. coli are reported from sciaenids and cat fish for the first time in this country.

Studies on the suitability of producing value-added products from silver carp, Hypophthalmichthys molitrix

Silver carp, Hypophthalmichthys molitrix is contributing significantly to the total production of fish through aquaculture in Bangladesh. However, its low market price has become a serious concern to the fish farmers. The suitability of silver carp mince for the production of various value-added products (VAPs) - surimi, fish sausage, fish burger and fish stick was studied during April-September 2000 to ensure more appropriate and profitable utilization of silver carp. Surimi/frozen mince block was produced by washing the silver carp mince with 0.1% NaCl for 7-8 min (4-5 min agitation and 3-4 min settling). A two-step heating schedule for incubation at 50°C for 2 h and cooking at 95°C for 30 min gave high textured good quality consumer product. With the addition of cryoprotectants, surimi could be kept frozen for 5 months without loosing [sic] much of its textural and sensory qualities. Mince-mix and a batter with different ingredients and spices were formulated to produce fish burger using potato smash as the binding agent. Fish flake-mix and a batter with different ingredients and spices were formulated to prepare fish stick using both potato starch and potato smash as filler ingredients. Unwashed and washed frozen mince block or fresh flesh of silver carp was used to prepare fish sausage by heating at 100°C for 1 h after incubating at 50°C for 2 h. A spice-mix formulated with various local spices at the rate of 1.0-1.2% gave good texture and flavor to the sausage. A good-appeared sausage-pink color was developed by combining three food-grade colors of asthaxanthin. Products prepared with potato starch, potato smash and rice smash had an acceptable bacterial load in refrigeration (5°C) for up to 8 days and in room temperature (28°C) for up to 3 days. No coliform bacteria were found in the products prepared.

Improved handling and preservation of freshwater giant prawn, Macrobrachium rosenbergii for producing safe and wholesome products

Studies were undertaken to evaluate the quality changes in freshwater giant prawn, Macrobrachium rosenbergii during various storage conditions of handling and preservation and producing safe and quality products. The samples kept in ice immediately after catch with head-on and head-less condition were found to be acceptable for 6 days and 7 days, respectively. Delaying of icing considerably shortened the shelf-life. The pH value increased from 6.36 to 8.0 after 10 days in ice. The initial average TVB-N value of sample increased from below 10 mg/100 g to 25 mg/100 g with the lapse of storage period. The Ca++ ATPase activity in presence of 0.1M KCl slightly decreased at the end of 10 days of ice storage. Immediately after harvest, initial aerobic plate count (APC) was 2.88x10^6 CFU/g which gradually increased to 1.12x10^8 CFU/g after 6 days in ice storage and showed early signs of spoilage. Initial bacterial genera in the prawn iced at 0 hours were comprised of Coryneform (22.21 %), Bacillus (7.40%), Micrococcus (11.11 %), Achromobacter (48.14%), Flavobacterium/Cytophaga (7.40%), Pseudomonas (3.70%) and Aeromonas (3.70%). During ice storage Coryneforms and Bacillus were always dominating along with less prominent ones - Micrococcus, Achromobacter and Flavobacterium. Studies were conducted on the stability of myofibrillar protein of M. rosenbergii under different storage and pH conditions. The influence of a wide range of pH on the remaining Ca++ ATPase activity of M. rosenbergii muscle myofibrils after storage at -20°C for 2 days, at 0°C for 2 days and at 35°C for 30 minutes demonstrated that ATPase activities were lower in acidic and alkaline pH regions and the activity remained relatively high. Mg++ ATPase activities both in presence and absence of Ca++ remained high at neutral pH compared to those of acidic and alkaline region. The solubility of myofibrillar protein decreased gradually both in acidic and alkaline pH regions. The study also examined the bacteriological quality of freshly harvested M. rosenbergii, pond sediment and pond water from four commercial freshwater prawn farms at Fulpur and Tarakanda upazilas in the district of Mymensingh. The study included aerobic plate count (APC), total coliform count, detection, isolation and identification of suspected public health hazard bacteria and their seasonal variation, salt tolerance test, antibiotic sensitivity test of the isolates and washing effect of chlorinated water on the bacterial load in the prawn samples. APC in sediment soil and water of the farm and gill and hepatopancreas of freshly harvested prawns varied considerably among the farms and between summer and winter season. The range of coliform count in water, gill and hepatopancreas ranged between 6 - 2.8x10^2 CFU/ml, 1.2x10^2 - 3.32x10^2 CFU/g and 1.43x10^2 - 3.89 x10^3 CFU/g, respectively. No coliform was detected in pond sediment sample. Suspected health hazard bacteria isolated and identified from pond sediment, water, gill and hepatopancreas included Streptococcus, Bacillus, Escherichia coli, Klebsialla, Salmonella, Staphylococcus, Pseudomonas and Aeromonas. Bacillus, Salmonella and Staphyloccus [sic], and were found to be highly salt tolerant and capable of growing at 10% NaCl. The antibiotic discs with different concentration of antibiotics were used for the sensitivity test. The organisms were found to be most sensitive against Tetracyclin and Gentamycin.

A bacteriological study of the natural flora of edible oyster, Crassostrea madrasensis

The total viable bacterial populations in the oysters and the sea water from the edible oyster farm at Tuticorin were in the range of 10 super(3) to 10 super(4) per ml and 1 super(2) to 10 super(3) per ml respectively. The maximum most probable number of faecal coliform recorded during the one year period of study of both the oysters and seawater were 33 per 100 ml. Pathogenic bacteria (Salmonella sp., Vibrio cholerae, coagulase positive staphylococci and faecal streptococci were absent in oysters and farm water. Study of 197 (98 taken from oyster liquid and 99 from oyster farm water) randomly isolated cultures indicated that gram negative asporogenus rod-like bacteria of the Vibrio, Flavobacterium, Achromobacter and Pseudomonas groups were the dominant flora of the oyster liquid as well as seawater.

Studies on the ice storage characteristics of blood clam Anadara granosa meat

Ice-storage study of blood clam (Anadara granosa) meat in direct contact and out of contact (in 200 gauge polyethylene bag) with ice was taken up to assess the amenability of the meat to icing. Changes in moisture, total protein, non-protein nitrogen, α amino nitrogen, total volatile base nitrogen, glycogen, free fatty acid, peroxide value, total bacterial count and coliform count were followed every day. The raw and cooked meat were also subjected to organoleptic evaluation. The study showed that the clam meat can be ice-stored in very good condition out of contact with ice in polyethylene packets for 4 days and in direct contact with ice for 2 days.

Cultural conditions of arylsulfatase activity in Escherichia coli

Arylsulfatase activity and growth were estimated in Escherichia coli, isolated from marine sediment. Maximum activity was observed at pH 6.6 whereas the maximum growth was at pH 5.6. 2x10ˉ³ M is the optimum substrate concentration for the highest level of enzyme activity/synthesis as well as for its growth. In general higher substrate concentration tended to inhibit enzyme activity and also the growth of the bacterium. Maximum growth and highest enzyme activity occurred at 29°C and above this temperature decreased both of them. Besides these, glucose, sodium sulfate, sodium chloride, sodium dihydrogen phosphate, sodium acetate and ammonium chloride at higher concentrations were inhibiting the enzyme activity and growth. Above 0.2% of glucose, 3% of sodium chloride, 10x10ˉ³ M concentrations of sodium sulfate, sodium dihydrogen phosphate, sodium acetate and ammonium chloride inhibited the activity and growth also. These observations indicate that, to generalize a compound as inhibitor or activator it is difficult since this depends not only on its concentration but also on the source of the enzyme when more than one type is encountered in nature.

Studies on cultural conditions of marine Chromatium buderi Truper and Jannasch 1968

Photosynthetic characteristics of a purple sulfur bacterium, Chromatium buderi, cultured under different ranges of pH, temperature, light intensities and ammonium chloride concentrations were examined. Maximum bacteriochlorophyll a synthesis was observed at pH 6.5 whereas the optimum growth was at pH 8.0. In general, higher temperature tended to inhibit the chlorophyll a synthesis and growth. 30°C is the optimum temperature both for chlorophyll a synthesis and growth. At 25µE mˉ²Sˉ¹ the bacteriochlorophyll a content and growth attained maximum level. The response to this low light intensity is an adaptation that ensures a high photosynthetic rate for the purple sulfur bacterium that usually occurs in dimly lit environment. Besides these, ammonium chloride at low concentration enhances both chlorophyll a synthesis and growth. Above 0.5% of it causes the nitrogen-chlorosis and also retards the growth of the bacterium. Possible chemical and structural mechanisms involved are discussed.

Inactivation of Vibrio parahaemolyticus in drinking water

A study was conducted in the Cochin area of India to determine the effect of drinking water on Vibrio parahaemolyticus, a bacterium that contaminates fish harvested from marine and estuarine environments. Times of fresh-water exposure required to inactivate these bacteria are given. Findings indicate that the washing of fish and equipment used to handle the fish in drinking water may decrease in the number of viable Vibrio cells and thus aid in prevention of food poisoning.

Microbiological quality study of Macrobrachium rosenbergii (de Man 1879) during storage at -20°C temperature

The shelf life of fresh water prawn Macrobrachium rosenbergii by applying low temperature was investigated. M. rosenbergii preserved at -20°C was subjected for quality assessment before storage and at 15, 30, 45, and 90 days of storage period. The quality assessments as done microbiological viz. total bacterial count (TBC), total mould count (TMC), total yeast count (TYC), total coliform count (TCC) and salmonella count. All the samples were acceptable during 90 days because the upper limit of all spoilage indicator was not exceeding within the experimental time period.

Effect of gamma radiation in combination with freezing on the microbiological changes in frozen shrimp Penaeus monodon

In this study gamma radiation (3, 6 and 9 kGy) in combination with low temperature (-20°C) were applied to retain the quality and shelf-life of shrimp, Penaeus monodon for a longer period. The quality was assessed by monitoring microbiological changes (TBC, TMC, TYC, TCC and Salmonella count) in irradiated and non-irradiated (control) samples. Among microbiological indicators of spoilage, total bacterial count (TBC) values for irradiated shrimps were found to be 1875, 1625 and 1525 cfugˉ¹ of sample at 3, 6 and 9 kGy respectively after 90 days whereas for non-irradiated samples it was found 2475 cfugˉ¹ of sample. Total moulds count (TMC) value for non-irradiated samples after 90 days were found 425 cfugˉ¹ sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 275, 250 and 200 cfugˉ¹ sample respectively. Total yeast count (TYC) value for non-irradiated samples after 90 days were found 4125 cfugˉ¹ sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 2850, 2150 and 1725 cfugˉ¹ sample respectively. Total coliform count and Salmonella count showed that those were absent during 90 days storage period. From this study, it was clear that gamma radiation in combination with low temperature showed shelf-life extension (90 days) in each dose of radiation used but during the use of 9 kGy radiation, Penaeus monodon showed best quality.

Study of physicochemical, microbial and sensory properties of surimi produced from black mouth croaker (Atrobucca nibe) at freezing condition (-18ºC)

Black mouth croaker (Atrobucca nibe) is considered as a new valuable fish stock in the Oman Sea. In this study, surimi was manufactured from nonmarket size of the fish, manually and different cryoprotectant agents were added to the surimi. Finally changes in physiochemical, microbiological and sensory quality, characteristics of the surimi and kamaboko gel samples were assessed during 6 months at freezing storage (-18ºC). Surimi samples with the addition of Iranian tragacanth gum (TG), xanthan gum (XG), chitosan (CS) and whey protein concentrate (WPC) at 1% (w/w) were prepared to evaluate their impacts as a cryoprotectant on the surimi, individually. The results showed that the whiteness and lightness indexes in all surimi samples were gradually decreased during frozen storage. This trend of decreasing was more intensity in the control sample from 61.08±0.131 to 54.21±0.067 was recorded (p<0.05). Water holding capacity (WHC) in all treatments was decreased during 6 months. The lowest WHC (g/g) was obtained in the surimi without cryoprotectants and maximum WHC was measured in Tcs and Twpc samples, respectively (p<0.05). The lowest breaking force was calculated in Txg (166.00±22.627 g) and Tc (271.50±263.16 g) during 6 months at frozen storage, respectively (p<0.05), while Twpc treatment with slight variations showed the highest breaking force (p<0.05). Also, the lowest gel strength was obtained in Txg (68.22±6.740 g.cm) after 6 month of frozen storage (p<0.05). All Kamaboko surimi gels texture profile analysis parameters decreaced with increasing shelf life. This decreasing trend in the control sample was more severe. Floding results were reduced in all samples during storage (p<0.05). The best protective results probably were obtained in WPC, chitosan and commercial cryoprotectant agents, respectively due to protein stabilization of myofibrillar proteins and the protein-protein network structure, leading to the formation of surimi gel with strong textural properties during frozen conditions. The average number of surimi polygonal structures were significantly decreased (number per mm2) and their area were significantly increased (μm2) in all treatments (p<0.05). With increasing storage time, moisture, protein contents and pH were decreaced. Maximun TVB-N index was calculated in Tc (7.93±0.400 mg/100g) and Txg (7.88±0.477), respectively (p<0.05). TBRAs index was increased in all treatments during frozen storage, while this trend was reached in maximum value in Tc (p<0.05). Sensory evaluation of the fish finger quality characteristics (color, odor, texture and overall acceptability) preapare from frozen black mouth croaker surimi was decreaced during 6 month frozen storage. After the period of frozen storage the highest quality scores were measured in Twpc, Tcs and Tcc samples, respectively (p<0.05). In this study, coliform bacteria were not found in all treatments during frozen storage. The surimi sample containing chitosan showed lower mesophilic and psychrotropic bacteria (log cfu/g) than other treatments during frozen storage (p<0.05). Salt-soluble proteins extractions of all treatments were decreased during frozen storage. This decreacing trend was highest in Tcs (45.74±0.176%) and lowest in Tc treatments after 6 month of frozen storage (29.92±0.224%) (p<0.05). Although commercial cryoprotectant agents were successful in limiting the denaturation of proteins but sugar contents were not accepted for diabetics or those who disagree with the sweet taste and high calorie food. Hence, commercial cryoprotectant agents can be replaced with whey protein concentrate and chitosan at 1% level (w/w) consider that they were showed proper protection of the surimi myofibrillar proteins during storage.

Determination of proximate composition, shelf life and fatty acid profiles of breaded kilka (Clupeonella cultriventris) during frozen storage

The present study aimed production of a new product with various texture and sensory properties in chase of the impetus for increasing human consumption considering suitable resources of Kilka fish in Caspian Sea. Following deheading, gutting, and brining, common Kilka were battered in two different formulations, i.e. simple batter and tempura batter, via automated predusting machinery and then, they were fried through flash frying for 30 seconds at 170°C in sunflower oil after they were breaded with bread crumbs flour. The products were subjected to continuous freezing at -40°C and were kept at -18°C in cold storage for four months once they were packed. Chemical composition (protein, fat, moisture, and ash), fatty acid profiles (29 fatty acids), chemical indices of spoilage (peroxide value, thiobarbituric acid, free fatty acids, and volatile nitrogen), and microbial properties (total bacteria count and coliform count) were compared in fresh and breaded Kilka at various times before frying (raw breaded Kilka), after frying (zero-phase), and in various months of frozen storage (phases 1, 2, 3, and 4). Organoleptic properties of breaded Kilka (i.e. odor, taste, texture, crispiness, cohesiveness of batter) and general acceptability in the phases 0, 1, 2, 3, and 4 were evaluated. The results obtained from chemical composition and fatty acid profiles in common Kilka denoted that MUFA, PUFA, and SFA were estimated to be 36.96, 32.85, and 29.12 g / 100g lipid, respectively. Levels of ù-3 and ù-6 were 7.6 and 1.12 g / 100 gr lipid, respectively. Docosahexaonoic acid (20.79%) was the highest fatty acid in PUFA group. ù-3/ù-6 and PUFA/SFA ratios were 7.6 and 1.12, respectively. The high rates of the indices and high percentage of ù-3 fatty acid in common Kilka showed that the fish can be considered as invaluable nutritional and fishery resources and commonsensical consumption of the species may reduce the risk of cardiovascular diseases. Frying breaded Kilka affected overall fat and moisture contents so that moisture content in fried breaded Kilka decreased significantly compared to raw breaded Kilka, while it was absolutely reverse for fat content. Overall fat content in tempura batter treatment was significantly lower than that of simple batter treatment (P≤0.05). Presence of hydrocolloids, namely proteins, starch, gum, and other polysaccharides, in tempura batter may prohibit moisture evaporation and placement with oil during frying process in addition to boosting water holding capacity through confining water molecules. During frying process, fatty acids composition of breaded Kilka with various batters changed so that rates of some fatty acids such as Palmitic acid (C16:0), Stearic acid (C18:0), Oleic acid (C18:1 ù-9cis), and linoleic acid (C18:3 ù-3) increased considerably following frying; however, ù-3/ù-6, PUFA/SFA, and EPA+DHA/C16:0 ratios (Polyan index) decreased significantly after frying. ù-3/ù-6, PUFA/SFA, and EPA+DHA/C16:0 ratios in tempura batter treatment were higher than those of simple batter treatment which is an indicator of higher nutritional value of breaded Kilka with tempura batter. Significant elevations were found in peroxide, thiobarbituric acid, and free fatty acids in fried breaded Kilka samples compared to raw samples which points to fat oxidation during cooking process. Overall microorganism count and coliform count decreased following heating process. Both breaded Kilka samples were of high sanitation quality at zero-phase according to ICMSF Standard. The results acquired from organoleptic evaluation declared that odor, cohesiveness, and general acceptability indices, among others, had significant differences between the treatments (P≤0.05). In all evaluated properties, breaded Kilka with tempura batter in different phases gained higher scores than breaded Kilka with simple batter. During cold storage of various treatments of breaded Kilka, total lipid content, PUFA, MUFA, ù-3, ù- 3/ù-6, PUFA/SFA, Polyen index decreased significantly. The mentioned reductions in addition to significant elevation of spoilage indices, namely peroxide, thiobarbituric acid, and free fatty acids, during frozen storage, indicate to oxidation and enzymatic mechanism activity during frozen storage of breaded Kilka. Considering sensory evaluation at the end of the fourth month and TVB-N contents exceeded eligible rate in the fourth month, shelf life of the products during frozen storage was set to be three months at -18°C. The results obtained from statistical tests indicate to better quality of breaded Kilka processed with tempura batter compared to simple batter in terms of organoleptic evaluation, spoilage indices, and high quality of fat in various sampling phases.

Effect of thawing methods on the chemical, biochemical, microbiological and sensory indices of Caspian Sea kutum (Rutilus frisii kutum) and rainbow trout (Oncorhynchus mykiss)

Effects of different thawing method i.e. in a refrigerator, in water, at air ambient temperature and in a microwave oven on proximate, chemical (PV, TBA, FFA, TVB-N, SSP, FA), biochemical (pH, WHC,ThL), microbial (total viable, psychrotrophic, coliform, Shewanella and yeast-mould count) and sensory analysis were carried out on frozen whole Caspian sea Kutum (Rutilus frisii kutum) and Rainbow trout (Oncorhynchus mykiss) carcasses. The values of ash, protein, SSP, WHC, PUFA, PUFA/SFA. EPA+DHA/C16:0, pH, and microbial count of thawed samples decreased significantly while fat, PV, TBA, FFA, TVB-N, SFA and MUFA increased compared to the fresh fish (unfrozen) as control samples. Also, sensory evaluation all of thawed samples showed a significant (p<0.05) quality loss compared to the fresh fish as control samples. The lowest chemical and biochemical values as well as microbial growth were determined in water thawed samples. Therefore, based on this study thawing in water is most suitable for frozen whole rainbow trout.

The effect of spirulina (fresh and dry) on some biological factors in Penaeus semisulcatus larvae

Spirulina is a filamentous cyanobacteria with many applications in food and drug industries, as a food in human, aquaculture, vet and poultry industries… . Semi and mass culture of Spirulina carries out in different countries. This study was carried out in five phases in order to produce this microalga in Iran. The first phase, Spirulina pure stock was imported from Indonesia. After identification of species, it was cultured in laboratory until we took 20 liters of biomass. The semi-mass culture was carried out in green house. Cell concentration and size of Spirulina were recorded during culture daily and their growth rates were calculated. After two weeks, when the size of Spirulina was suitable, biomass of Spirulina was harvested then accumulated Spirulina weighted and dried in 24 hours in laboratory. In order to microbiological study, the samples of Spirulina (dry and fresh) were cultured on blood agar medium and coliforms were counted. The chemical composition of produced Spirulina was measured by standard methods. Fatty acid and amino acid profiles were acquired by GC and HPLC instruments, respectively. The amount of chlorophyll in Spirulina was determined by spectroscopy method. Also astaxanthin pigment as an important carotenoid was measured by HPLC in Spirulina and Penaeus semisulcatus larvae fed on Spirulina. At final phase of this project, larva fed on produced Spirulina (biomass and dry powder) was compared to Z plus, microencapsulated Spirulina (M.C.F) and Chaetoceros algae as control. This experiment was carried from zoa to early post larvae stage then survival and growth rate of larvae were recorded. The growth rate of larvae was evaluated with ANOVA test and survival rate of treatments was assessed by Log Rank (Mantel –Cox) test. Also during larvae stage, two parameters of water such as nitrate and nitrite were measured in zoa, mysis and post larvae stages. The results of this study were shown that colifom counts were 1.85×106 and 92.3×105 coliform per ml in fresh and dry spirulina, respectively. Protein percent of dry spirulina was 50.93 % (dry weight) and the amount of astaxanthin in spirulina and larvae fed on spirulina were 0.21 and 0.01 mg/kg, respectively. The most survival rate of larvae were observed in zoa III (88.8%) with Z plus supplement treatment, in mysis III (76.5%) combination of Z plus and dry spirulina in comparative between treatments. Larvae growth (4.5mm) of control in early post larvae was the best.

Gross clinical signs and haematological changes associated with artifical infection of Edwardsiella tarda in Koi Carp

The occurrence of diseases is a significant setback for successful aquafarming. One of the common fish bacterial disease syndromes, Edwardsiellosis is caused by Edwardsiella tarda, a gram-negative, rod shaped bacterium associated with several diseases of marine and fresh water fish. In this study, an attempt was made to observe and analyze the onset of clinical symptoms and certain haematological parameters in Koi Carp, Cyprinus carpio L., following artificial infection with Edwardsiella tarda. The disease progress was observed and the clinical symptoms were monitored over a period of 15 days following infection. Fish were sampled at three day intervals to analyse the haematological parameters: total erythrocyte counts (RBC), total leucocyte counts (WBC), haemoglobin content and differential leucocyte count. Clinical symptoms observed included: erratic swimming behaviour, loss of appetite, haemorrhages, dropsy and exophthalmia. There was a significant decrease in the total RBC and haemoglobin levels by the 3rd and 6th day post infection, and an increase thereafter. WBC counts were higher in all infected groups in comparison to the control group. A significant increase in the number of neutrophils was found in the infected group up to the 9th day and a decrease thereafter. The lymphocyte number was significantly less up to the 12th day while the monocyte counts were significantly higher up to the 12th day post infection. The results showed that the bacterium, E. tarda, is pathogenic to Koi Carp. The hematological changes and clinical signs in infected fish reported in this paper will be helpful in the identification and the control of this infection.